fix(knx): writing integer 0

shard.yml

@@ -1,5 +1,5 @@
 name: knx
-version: 1.2.3
+version: 1.2.4
 crystal: ">= 0.36.1"
 
 dependencies:

spec/knx_spec.cr

@@ -78,4 +78,14 @@ describe "knx protocol helper" do
     cemi = input.read_bytes(KNX::CEMI)
     cemi.to_slice.should eq cemi_raw
   end
+
+  it "should encode / decode a Group Write 0" do
+    datagram = knx.action("4/1/7", 0, source: "0.0.0")
+    cemi_raw = "1100bce000002107010080".hexbytes
+    datagram.cemi.to_slice.should eq(cemi_raw)
+
+    input = IO::Memory.new(cemi_raw)
+    cemi = input.read_bytes(KNX::CEMI)
+    cemi.to_slice.should eq cemi_raw
+  end
 end

src/knx.cr

@@ -49,17 +49,21 @@ class KNX
           when Bool
             data ? Bytes[1] : Bytes[0]
           when Int
-            io = IO::Memory.new
-            io.write_bytes(data, IO::ByteFormat::BigEndian)
+            if data.zero?
+              Bytes[0]
+            else
+              io = IO::Memory.new
+              io.write_bytes(data, IO::ByteFormat::BigEndian)
 
-            bytes = io.to_slice
-            index = 0
-            bytes.each_with_index do |byte, i|
-              next if byte == 0
-              index = i
-              break
+              bytes = io.to_slice
+              index = 0
+              bytes.each_with_index do |byte, i|
+                next if byte == 0
+                index = i
+                break
+              end
+              bytes[index..-1]
             end
-            bytes[index..-1]
           when Float, String, Time
             KNX.datapoint(data).to_bytes
           when Datapoint